Squeeze the lemon. Dice the smoked bacon and onion.
In a bowl, mix the diced bacon, onion, tomato paste, salt, pepper, half of the lemon juice, sugar, and whipped cream into a paste.
Wash the fish fillets. Drizzle with the remaining lemon juice and sprinkle lightly with salt.
Spread the bacon mixture on one fish fillet. Layer a second fillet on top and spread more bacon mixture on it. Repeat with remaining fillets to make 4 stacks. Scatter breadcrumbs over each stack and dot with flakes of butter.
Place the assembled fish stacks in a well-greased grill pan or casserole dish and bake in a preheated oven at 220°C (428°F), or 200°C (392°F) for fan ovens, for 18 to 25 minutes until the top is crispy.
While the fish bakes, peel the potatoes. Bring salted water with the bay leaf to a boil, add the potatoes, and cook for 20 to 30 minutes (depending on potato size) until tender.
Serve the fish with the potatoes and, if desired, fresh vegetables or green salad.